Bushing for pressure loaded gear pump having a tapered journal surface



Jan. 27, 1959 J. F. MURRAY ET AL 2,870,719

BUSHING FOR PRESSURE LOADED GEAR PUMP HAVING A TAPERED JOURNAL. SURFACE Filed Oct. 4, 1955 I s Sheets-Sheet 1 RD N N N I U N 0 a o N v 3 E Fl IN V EN TORS JOHN F. MURRAY JOHN A. WOTRING ATT RNEYS Jan. 27, 1959 J. F. MURRAY ET AL BUSHING FOR PRESSURE LOADED GEAR PUMP HAVING A A TAPERED JOURNAL SURFACE Filed Oct. 4, 1955 3 Sheets-Sheet 2 46 6 n 2| 5O V 7 66 Isa/"58 6| 23 76 31 Iig-Z 3o 21 48a 19 u 48 2o v 53 Z 3 1* 23 49a INVENTORS JOHN F. MURRAY BY JOHN A. WOTRING by A? ORNEYS 1959 J. F. MURRAY ET AL 2, 7

BUSHING FOR PRESSURE LOADED GEAR PUMP HAVING A TAPERED JOURNAL SURFACE Filed Oct. 4, 1955 3 Sheets5heet 3 INVENTORS JOHN F. MU RRAY JOHN A. WOT RING ATTO R EYS Unite States Patent BUSHING FOR PRESSURE LOADED GEAR PUMP HAVING A TAPERED JOURNAL SURFACE John F. Murray, Macedonia, .and John A. 'Wotring, Painesville, Ohio, assignors to Thompson Products, Inc., Cleveland, Ohio, a corporation of Ohio Application October 4, 1955, Serial No. 538,450

20 Claims. (Cl. 103-126) This invention relates generally to pressure loaded gear pumps and more particularly to a pressure loaded gear pump having a movable end plate means loaded by pressurized fluid at pressures generated by the pump and specifically characterized by the provision of bearing surfaces between end plate means and pump gears divergent in the direction of the adjoining gear face, thereby to provide a gradually increasing clearance space along the length of the gear shaft.

In one form of pressure loaded gear pump, the rotatable pumping member takes the form of a gear having tubular shaft extensions rotatably journaled in axially spaced bearings. Thus, the gear shaft is supported in the manner of a beam.

In pumping fluid, the load which is imposed upon the gears is transmitted to a portion of the assembly corresponding to the center of the beam. Accordingly, the stress concentrations which are present in the pump produce a deflection of the beam. Additionally, there may be some tendency to a slight misalignment in end to end direction.

Because the operating phenomena referred to in the foregoing remarks are present in gear pump structures, increased capacity requirements and higher operating speeds have produced problems which are directly attributable to the foregoing characteristics. For example, there may be a concentration of load at the inner portion of the supporting member which results in the generation of heat and which further results in increased friction and wear.

According to the principles of the present invention, means are provided wherein bearing surfaces are formed between a bushing or end plate means and a gear. The bearing surface is provided with a divergent inclination in the direction of the adjoining gear side face, thereby providing a gradually increasing clearance space along the length of the gear shaft.

There is thus provided a clearance space which is generally annular in configuration and somewhat conical, having its widest opening at the inner portion of the support. By virtue of such provision, load concentration is cut down at the inner portion of the supporting member. Additionally, the clearance space facilitates the introduction of coolant and lubricant into the journal surface and greatly facilitates the dissipation of thermal energy.

It is an object of the present invention, therefore, to provide an improved pressure loaded gear pump.

Another object of the present invention is to provide improved support means for the impeller of the pressure loading gear pump.

Yet another object of the present invention is to provide a beam type support for a gear type impeller wherein the concentration of load at the inner portion of the supporting member is reduced.

A further object of the present invention is to provide a bearing support means for a pressure loaded gear pump which has improved means to facilitate the dissipation of heat energy.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment of a pressure loaded gear pump embodying the principles of the present invention is shown by way of illustrative example.

On the drawings:

Figure 1 is a cross sectional view of a pressure loaded gear pump incorporating the improved bushing or end plate means of the present invention;

Figure 2 is a fragmentary cross sectional view showing in greatly exaggerated form the structural characteristics of the bushings or end plate means provided in accordance with the principles of the present invention;

Figure 3 is a view similar to Fig. 2 but illustrating an alternative embodiment of the invention disclosed herein;

Figure 4 is a view similar to Figs. 2 and 3 but showing yet another structural embodiment of the principles of the present invention;

Figure 5 is an end elevational view of a movable pressure loaded bushing provided in accordance with the principles of the present invention;

Figure 6 is a cross sectional view taken substantially on line VlVI of Fig. 5;

Figure 7 is an end elevational view of a fixed bushing provided in accordance with the principles of the present invention;

Figure 8 is a cross sectional view taken substantially on line VIlIVIII of Figure 7.

As shown on the drawings:

In order to most clearly demonstrate the operating environment in which the principles of the present invention find greatest utility, the principles of the presentinvention are disclosed in connection with a pressure loaded gear pump indicated generally by the reference numeral 10 and having a casing 11 formed from a plurality of fastened together sections. At one end of the casing 11 there is provided a housing section 12 forming a pump inlet 13 and providing a volute pumping chamber 14 in which is rotated a centrifugal impeller 16 for initially pressurizing inlet fluid. From the centrifugal impeller 16, the fluid is discharged through the casing 11 to the respective inlet portions of a plurality of gear pumps all operatively enclosed within the casing 11 and indicated generally by the reference characters A, B and C.

With minor exceptions, each respective gear pump, A, B and C is identical in structure and operation and, accordingly, description of a single unit will suflice for purposes of this disclosure and like reference numerals will be applied wherever possible.

Each of the gear pumps includes a driver gear 17 and a driven gear 18 rotatably intermeshed and operated within a pumping chamber formed by a pair of overlapping generally circular bores 19 and 20 formed within corresponding sections of the casing 11. The pumping chambers have an inlet supplied with fluid initially pressurized by the impeller 16 and an outlet through which fluid is delivered.

Adjacent the bore 19 and 20 are smaller sized bores 21 and 22 respectively, on one side and 23 and 24 respectively, on the other side.

All of the driver gears 17 of the pumps A, B and C and the impeller 16 of the centrifugal inlet stage are driven by a common driving means which includes a separate driving member 26 splined as at 27 to a shaft extension 28 formed on the driver gear 17 of the pump C Patented Jan. 27-, 1959' and splined as at 29 to a quill shaft 30 which extends freely through a bore 31 formed in the driver gear 17.

The quill shaft 30 is splined as at 32 to a driver gear of the pump 'B and is splined as at 33 to the gear of the pump A.

A second quill shaft 34 is splined as at 36 to the quill shaft 30 and is connected as at 37 to a gear 38 journaled on a shaft extension 39 formed on the end of the driver'gear 17 of the pump A. The gear 38 is part of a gear train and meshes with a gear 40 journaled on a shaft extension 41 formed on the driven gear 18 of the pump A and connected to the centrifugal impeller 16. By virtue of such relation, the centrifugal impeller 16 is rotatably driven at a higher speed than the gears of the pumps A, B and C.

A shear section 42 is formed in the quill shaft 34, ashear section 43 is formed in the quill shaft 30, a shear section 44 is formed in the shaft extension 46 of the driver gear 17 of the pump B, and a shear section 47 is formed in the driving member 26 to permit continued operation of diflerent pump units in the event of binding or seizure of one of the pump units.

Received within the bores 21 and 22 of the casing 11 for each respective pump A, B and C and for each respective driver gear 17 and driven gear 18 is a fixed bearing indicated generally at 48.

Received within each respective bore 23 and 24 of each pump A, B and C for a corresponding driver gear 17 and a driven gear 18 is a movable pressure loaded bearing or bushing indicated at 49. The structural details which characterize the fixed and movable bearings or bushings 48 and 49 will be more clearly understood upon making reference to Figs. 2-8.

Referring first of all to Figs. 7 and 8, it will be noted that the fixed bushings 38 each comprise a generally tubular body portion 56 terminating at one end in a radially outwardly extending flange 51 having a front sealing face 52 formed thereon for engaging an adjoining side face of a corresponding driver or driven gear 17 and 18. i I

As shown in Fig. 7, the sealing face 52 is intersected by a bore 53 counterbored as at 54. The walls of the bore 53 provide a bearing surface for journaling the confronting bearing surface 56 formed on a shaft extension 57 of the corresponding driver or driven gear 17 and 18. As is most clearly illustrated in Fig. 2, the bearing surfaces provided by the walls of the bore 53 are'divergently inclined as at 58 in the direction of the adjoining gear side face, thereby providing a gradually increasing clearance space along the length of the gear shaft. The gradually increasing clearance space 58 provided in the bearing surface has the effect of re-' moving center stress concentration on the beam supported gears and is preferably at an inclination in the order of to ten thousandths of an inch.

The tapered clearancespace 58 terminates in the annular counterbore 54 cut of a large enough diameter to completely eliminate radial load on the'fixed bearings 48 immediately adjacent the adjoining side faces of the gears 17 and 18.

The clearance space 58 will have the effect of facilitating the dissipation of heat by permitting coolant and lubricant in the form of the fluid medium being pumped to flow into the space and flood the bearing surface. To further assist in this action, one or more axially extending grooves 59 are formed in the bearing surfaces. The grooves 59 may be blind ended as at 68 toinsure that an adequate supply of coolant and lubricant is maintained at the journal surface.

The movable pressure loaded bushing 49 has a front sealing face 61 and a rear motive surface 62 formed on a flange 63 integrally formed on the end of a tubular extension 64. The sealing face 61 engages in adjoining side face of a corresponding gear 17 or 18 while the motive surface 62 is spaced from an adjoining wall 66 4 provided by the casing 11, thereby to form a pressure control chamber 67.

The outer periphery of the flange 63 and the outer periphery of the tubular extension 64 are generally con.- centric, thereby facilitating formation of the corresponding recesses 19 and 23 and 20 and 24 in the casing 11 in concentric disposition.

In order to proportionately modify the effective area on the motive surface 62 so that the pressure forces developed in the pumping chamber Will be exactly balanced by the thrust pressureexerted against the movable pressure loaded bushings 49 in the pressure control chamber 67, the motive surface 62 is particularly characterized by the provision of a generally circular axial extension or shoulder 68 which has its center eccentrically offset towards the inlet side of the pump, thereby to prescribe the inner periphery of the annular motive surface 62 which is offset towards the inlet side of the pump. Thus, the motive surface 62 is divided into a major area on the discharge side of the pump and a minor area on the inlet side of the pump, the total effective area of the motive surface 62 increasing proportionately from the inlet side of the pump to the discharge side of the pump so that a balancing thrust will be exerted upon the movable bushing 49.

A corresponding recess 70 is formed in the casing 11 to receive the axial extension or shoulder 68, however, a wide tolerance variation is afforded because the pressure in the control chamber 67 is sealed by the provision of O-ring members indicated at 71 and 72 respectively.

To transmit fluid at pump generated pressure to the pressure control chamber 67, the flange 63 is apertured as at 73 on the discharge side of the bushing 49.

' The sealing face 61 of the movable bushing 49 is intersected by a bore 74, the walls of which provide a bearing surface for engaging and journaling a confronting bearing surface 76 formed on a corresponding shaft extension of a gear 17 or 18. The bearing surfaces are particularly characterized by the provision of a divergent inclination in the direction of the adjoining gear side face, thereby providing a gradually increasing clearance space along the length of the gear .shaft to reduce the center load concentration. The tapered clearance ,space indicated in Fig. 2 by the reference numeral '77 terminates in an annular counterbore 78 formed in the sealing surface 61, thereby to remove all radial load from the movable bushing 49 adjacent the gear side face. I

The tapered clearance space 77 will have the effect of distributing coolant and lubricant to the bearing and journaling surface, however, to further facilitate the flooding of the bearing and journaling surface with coolant and lubricant, one or more grooves 79 blind ended as at 80 may be formed in the bearing surface 74 of the movable bushing 49.

It will be noted upon referring to Figs. 5 and 7 that each of the sealing faces 52 and 61 of the fixed and movable bushings 48 and 49 has formed on the inlet side a chamfered clearance indicated at 81 to facilitate filling of the spaces between the gear teeth and to improve the flow characteristics through the pump. Additionally, on the discharge side, the bushings 48 and 49 have trapping reliefs indicated at 82. To insure the adequate supply of coolant and lubricant to the counterbores 54 and 78 and the blind ended grooves 59 and 79 of the fixed and movable bushings 48 and 49, respectively, each is provided with a generally radially extending passageway 83 (Figs. '6 and 7) extending from the trapping re- ]ief 82 to the corresponding counterbores 54 and 78. Thus, fluid at full discharge pressurev is flooded into the bearing and journaling surfaces for cooling and lubricatmg purposes. 7

The sealing surfaces 52 and 61, if desired, may also be provided with an annular groove such'as is indicated at 84 0.1. the sealing su face 2 illust at in The se en g ro e 8 e nd from h rapp n re ief, 3. and i 19- cated radially outwardly of the root diameter of the gear teeth, thereby to intercommunicate the spaces between the gear teeth and tending to even out the distribution of pressure load.

In the alternative embodiment of Fig; 3, all of the structure thus far described is provided, however, to further increase the annular clearance space .58 and 77, the shaft extensions of the gear are provided with bearing surfaces 90 and which taper in a direction of the .gear

side faces, thereby to provide an enlarged annular conical clearance space as indicated at 91.

Although shown in greatly exaggerated form in Figs. 2 and 3, it will be appreciated by those versed in the art that the degree of inclination provided to afford the clearance space 77 on the movable bushing 49 and the clearance space 91 on the tapered surfaces 90 is preferably in the order of to ten thousandths of an inch.

In the alternative embodiment of Fig. 4, fixed bushings 48;: are provided and movable bushings 49a are provided. The bearing surfaces 53a and 74d of the respective fixed and movable bushings 48a and 49a are not specifically tapered, however, the confronting bearing surfaces 90a on the shaft extension are divergently inclined thereby to provide clearance spaces 91a.

Although various minor structural modifications might be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of our contribution of the art.

We claim as our invention,

1. A fluid pump of the type including a housing having an inlet and an outlet port formed therein, a rotatable pumping member journaled in said housing for transferring fluid from said inlet to said outlet, axially movable end plate means adapted to engage said pumping member in sealing relation and movable independently of said rotatable pumping member, a continuous generally annular motive surface on said end plate adapted in response to application of pressure thereto to urge said end plate toward said rotatable member to establish said sealing relation, conduit defining means for continuously communicating pressure generated by said pump to said motive surface, said motive surface having a generally circular outer periphery concentrically disposed with respect to the axis of rotation of the pumping member and a generally circular inner periphery eccentrically disposed with respect to the axis of said pumping member, said inner periphery having its center offset toward said inlet port, and means forming bearing and journaling surfaces between said rotatable pumping member and said movable end plate means provided with a divergent inclination extending in the direction of the engaging portions of said pumping member and said end plate means to provide an annular generally conical clearance space, reducing center load concentration.

2. A fluid pump having a suction side, a discharge side, a rotatable pumping member, an axially movable, pressure loadable end plate having a continuous graduated discharge pressure responsive motive surface, said motive surface having a major area and a minor area, said end plate being movable with respect to said pumping member and engageable in a surface opposite to said motive surface with an adjacent side face of said pumping member in sealing relation, the major area of said motive surface being located on said discharge side and the minor area of said motive surface being located on said suction side, conduit defining means for continuously communicating pressure generated by said pump to said motive surface, and means forming bearing and journaling surfaces between said end plate and said pumping member provided with a divergent inclination extending to said adjacent side face of said pumping member and forming an annular clearance space of divergent con- 6 figuration to reduce center loadconcentration andfacilitate heat dissipation.

3, In a pressure loadable bushing for establishing a sealing relation with the side face of an associated rotatable pumping member mounted on a shaft journaled in said bushing, said bushing being axially movable with respect to said rotatable pumping member, a sealing surface on said bushing generally concentric with said shaft and said pumping member and adapted to engage said pumping member side face in sealing relation, a unitary pressure responsive motive surface on said bushing oppositely located With respect to said sealing surface and asymmetrically disposed with respect to said sealing surface, said motive surface embracing the axis of said pumping member, conduit defining means for continuously communicating pressure generated by said pump to said motive surface, and a bearing surface on said bushing for journalling the pumping member, said bearing surface particularly characterized by the provision of a divergent inclination extending in the direction of said pumping member side face and forming a divergent annular clearance space at the journal for reducing center load concentration and for facilitating the dissipation of thermal energy. 1

4. In a pressure loaded pump of the type comprising a housing having an inlet and an outlet formed therein, a pair of intermeshing pumping gears rotatably journaled in said housing, an axially movable pressure loadable plate associated with each of said gears to rotatably journal said gears in said housing and having a forward sealing surface thereon adapted to engage the associated gear side face in sealing relation, each plate being axially movable with respect to its associated pumping gear, a motive surface on each plate oppositely disposed with respect to said sealing surface, conduit defining means for continuously communicating pressure generated by said pump to said motive surfaces to urge said plate forward surfaces into said sealing relation, and motive surface area defining means for restricting the area of each said motive surface so arranged that the area thereof exposed to pressure generated by said pump and lying adjacent the outlet of the pump is greater than the area exposed thereof adjacent the inlet side of the pump, and means forming bearing surfaces between said gears and said end plates rotatably journaling said gears in said housing, said bearing surfaces being characterized by the provision of a divergent inclination therein extending in the direction of said forward sealing surface to reduce center load concentration. 5. In a fluid pump of the type including-a housing havlng an inlet and an outlet port formed therein, a rotatable pumping member in said housing for transferring fluid from said inlet to said outlet and having bearing surfaces, axially movable end plate means having bearing surfaces for journaling said pumping member in said housing and having a sealing surface engageable with one side of said pumping member in sealing relation, said end plate being axially movable with respect to said pumping member, a motive surface on said end plate oppositely located with respect to said rotatable pumping member engaging surface and adapted in response to application of loading pressure thereto to urge said end plate toward said rotatable member to establish said sealing relation, and conduit defining means for continuously communicating loading pressure generated by:

said pump to said motive surface, said motive surface being generally annular and having a substantially circular outer periphery concentrically disposed with respect to the axis of rotation of the pumping member, said motive surface having an axial extension formed thereon having an outer periphery eccentrically disposed with re spect to said axis and having its center offset towards. said inlet port whereby said motive surface has a sub-- stantially lesser radial dimension adjacent said inlet port: than adjacent said discharge port so that upon applica tion of a uniform fluid pressure perunit area to said motive surface a graduated sealing force is provided having a minimum value adjacent said inlet and a maximum value adjacent said outlet, said bearing surfaces of said gears and said end plates means together forming a gradually increasing clearance space divergently inclined in the direction of said sealing surface to reduce center load concentration.

6. A high pressure pump including a body providing a pumping cavity with an inlet and an outlet, bearing means in said pumping cavity each defining an end plate portion and a tubular bearing portion eccentrically offset relative to said end plate portion toward the inlet of the pump to provide a face outwardly of the pumping cavity on the end plate portion which increases in width towards the pump outlet, said bearing means and said body together forming a chamber behind said end plate portions, means providing a passage in communication with the pump discharge and said chamber, whereby pressure forces in the pumping cavity tending to shift the end plate portions away from the pumping cavity will be balanced by pressure forces in said chamber which increase from the inlet to the outlet sides of the pump, and a bore in said bearing means for journaling a rotatable pumping member providing a bearing surface divergently inclined from said tubular bearing portion in the direction of said end plate portion to form a gradually increasing clearance space for reducing center load concentration.

7. In a high pressure pump including a body having a pumping cavity with an inlet and an outlet, a bearing means in said cavity having an end plate portion and a tubular bearing portion eccentrically displaced relative to said end plate portion toward the inlet of the pump to decrease the extent of exposed plate area in the region of the pump inlet, said bearing means and said body arranged to define a chamber behind said end plate portion, and means providing a passage in communication 1 with the pump discharge and said chamber, whereby balancing pressure loads are provided on both sides of the plate portion, and a bore in said bearing means for journaling a rotatable pumping member providing a bearing surface divergently inclined from said tubular hearing portion in the direction of said end plate portion to form a gradually increasing clearance space to reduce center load concentration.

j 8. In a high pressure pump, a housing having an inlet and an outlet and providing a pumping cavity, and a backing plate for said cavity in said housing, said backing plate having a pressure receiving back surface forming together with means including a portion of said housing a pressure control chamber, and means placing said pressure control chamber in pressure communication with said outlet, said back surface increasing proportionately in area from the pump inlet to the pump outlet for balancing unequal pressure forces in the cavity, said backing plate having an annular bearing surface formed therein for journaling said rotatable pumping member, said surface being divergently inclined in the direction of the pumping cavity to provide a gradually increasing clearance space to reduce center load concentration.

, 9. In a pump, a housing having an inlet and an outlet and providing a pumping cavity, a shiftable plate closing one end of said cavity in said housing and being subject to pressures in the cavity which increase towards the outlet side of the cavity, said shiftable plate forming together with means including a portion of said housing a pressure control chamber adjacent said cavity, a back face on said shiftable plate forming a wall of said pressure control chamber and having an eifective area increasing in size from the inlet to the outlet sides of the pump to produce balancing forces urging the plate towards the cavity in proportion to the unequal forces urgjournal surfaces.

j rotatable pumping member, said annular journaling sur- 'cylindrical journal surfaces, bearing means providing bearing surfaces for beam support and journaling of said impeller at its journal surfaces, and a divergent inclination formed in said surfaces forming diverging clearance spaces between said journal and bearing surfaces extending towards the impeller to reduce center load concentration adjacent said hub portion of said impeller.

11. In a pump as defined in claim 10, said divergent inclination being formed in said bearing surfaces of said bearing means. i Y

12. In a pump as defined in claim 10, said divergent 'inclination being formed in said journal surfaces of said rotatable impeller.

13. In a pump as defined in claim 10, said divergent inclination being formed in both of said bearing and 14. A fluid pump of the type including a housing having an inlet and an outlet port formed therein, a rotatable pumping member journaled in said housing for transferring fluid from said inlet to said outlet, end plate means adapted to engage said pumping member in sealing relation, and means forming bearing and journaling surfaces between said rotatable pumping member and said end plate means provided with a divergentinclination extending in the direction of the engaging portions of said pumping member and said end plate means to provide an annular clearance space of gradually increasing center load concentration between the bearing and the journal adjacent the gears.

16. In a gear pump, a rotatable gear having axially extending journals, bearing means providing a beam type support for said gear journals, said bearing means and said gear journals having bearing and journal surfaces provided with a divergent inclination extending in the direction of said gear to reduce center load concentration.

17. In a gear pump, a rotatable gear having oppositely extending axial journals, bearing means providing a beam type support for said gear journals, said bearing means and said gear having bearingand journalsurfaces provided with a divergent inclination extending in the direction of said gear to reduce center load concentration, said clearance space terminating in an annular recess formed to remove all radial load from the bearing and journal means immediately adjacent the adjoining gear side face.

18. In a gear pump, a rotatable gear having oppositely axially extending journals, bearing means providing a beam type support for said gear journals, said bearing means and said gear journals having bearing and journal surfaces provided with a divergent inclination extending in the direction of said gear to reduce center load concentration, said clearance space terminatingin an annular recess formed to remove all radial load from the extending axial journals, bearing means providing a beam type support for said gear journals, said bearing means and said'gear journals having bearing and journal surfaces provided with a divergent inclination extending in the direction of said gear to reduce center load concentration, said clearance space terminating in an annular recess formed to remove all radial load from the bearing means immediately adjacent the adjoining gear side face, and passage means communicating pump generated pressure into said annular recess to flood said clearance space with coolant and lubricant, said bearing surfaces being further provided with axially extending grooves to 'assist in flooding the bearing surfaces with coolant and lubricant.

20. .In a pump, a rotatable impeller having axially spaced journal surfaces on opposite sides of a point of load concentration, bearing means including a bushing on one side of said point of load concentration providing bearing surfaces for beam support and journaling of said impeller at its journal surfaces, and a taper formed in said bearing surface of said bushing forming diverging clearance spaces extending towards the impeller to reduce center load concentration, said taper terminating in an annular recess adjacent said impeller to remove locally bearing load on said bearing surface and means References Cited in the file of this patent UNITED STATES PATENTS 1,372,576 Tullmann Mar. 22, 1921 1,379,587 Fisher May 24, 1921 1,834,754 Whaley Dec. 1, 1931 2,322,004 Fast June 15, 1943 2,344,275 Straub Mar. 14, 1944 2,527,941 Lauck et a1. Oct. 31, 1950 2,676,548 Lauck Apr. 27, 1954 2,695,566 Compton Nov. 30, 1954 2,696,172 Compton Dec. 7, 1954 FOREIGN PATENTS 107,213 Austria Sept. 10, 1927 220,818 Switzerland July 16, 1942 789,907 France "1-..- Aug. 26, 1935 

